Is there a reason why the idea suggested just before the "Dumb investment certificate"[1] can't be implemented? It can be implemented like a Roth IRA (ie. a special account type). IRS would be in charge of keeping track of how much "dumb money" was "spent" in total, and all the issuer has to do is ensure the money came from a "dumb money" account.

[1] the paragraph starting with "A better approach might be to lower (or eliminate) the wealth bar for investing in private placements"